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<title>Issue 129: Need error indication from seekp() and seekg()</title>
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<p><em>This page is a snapshot from the LWG issues list, see the <a href="lwg-active.html">Library Active Issues List</a> for more information and the meaning of <a href="lwg-active.html#TC1">TC1</a> status.</em></p>
<h3 id="129"><a href="lwg-defects.html#129">129</a>. Need error indication from seekp() and seekg()</h3>
<p><b>Section:</b> 31.7.5.4 <a href="https://wg21.link/istream.unformatted">[istream.unformatted]</a>, 31.7.6.2.5 <a href="https://wg21.link/ostream.seeks">[ostream.seeks]</a> <b>Status:</b> <a href="lwg-active.html#TC1">TC1</a>
 <b>Submitter:</b> Angelika Langer <b>Opened:</b> 1999-02-22 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#istream.unformatted">issues</a> in [istream.unformatted].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#TC1">TC1</a> status.</p>
<p><b>Discussion:</b></p>
<p>Currently, the standard does not specify how seekg() and seekp()
indicate failure. They are not required to set failbit, and they can't
return an error indication because they must return *this, i.e. the
stream. Hence, it is undefined what happens if they fail. And they
<i>can</i> fail, for instance, when a file stream is disconnected from the
underlying file (is_open()==false) or when a wide character file
stream must perform a state-dependent code conversion, etc. </p>

<p>The stream functions seekg() and seekp() should set failbit in the
stream state in case of failure.</p>


<p id="res-129"><b>Proposed resolution:</b></p>
<p>Add to the Effects: clause of&nbsp; seekg() in 
31.7.5.4 <a href="https://wg21.link/istream.unformatted">[istream.unformatted]</a> and to the Effects: clause of seekp() in
31.7.6.2.5 <a href="https://wg21.link/ostream.seeks">[ostream.seeks]</a>: </p>

<blockquote>
  <p>In case of failure, the function calls <code>setstate(failbit)</code> (which may throw <code>ios_base::failure</code>).
  </p>
</blockquote>


<p><b>Rationale:</b></p>
<p>Setting failbit is the usual error reporting mechanism for streams</p>




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